This invention relates generally to a method for producing slabstock polyurethane foams and, more particularly, to the use of very low unsaturated polyether polyols for the production of slabstock polyurethane foams.
Polyols are generally defined as compounds that include a plurality of hydroxyl groups. Polyols having at least two isocyanate-reactive hydrogen atoms, particularly polyether polyols, are useful when combined with polyisocyanates to form polyurethanes. Polyols can be combined with polyisocyanates in the presence of catalysts and blowing agents to form either rigid or flexible foams. Flexible polyurethane foams are distinct from rigid foams. Flexible foams typically have a limited resistance to an applied load, are open-celled, permeable to air and are reversibly deformable. Flexible foams can either be formed in a discontinous molding process or through a continuous slabstock process. In the continuous slabstock process, typically, the components are rapidly mixed together and extruded onto a moving bed reactor where the foam is permitted to freely rise to its final height. After the foam has fully risen it is processed to the desired final dimensions. Flexible foams are particularly useful in seating applications, carpet padding and other applications requiring reversible deformation of the foam.
Two important properties of flexible slabstock foam are its indentation force deflection and resilience. Many current flexible slabstock foam formulations suffer from less than ideal indentation force deflection and resilience properties. It would be advantageous to provide a flexible slabstock formulation having improved indentation force deflection and resilience properties
In general terms, this invention provides a method for making a flexible slabstock polyurethane foam using very low unsaturated polyether polyols. The foam produced by the method has substantially improved indentation force deflection and resilience properties while maintaining the other physical properties of the foam when compared to foam made with a polyol having higher unsaturation levels. These improved properties greatly enhance the foam""s loadbuilding characteristics.
In one embodiment, the present invention is a method for the formation of a slabstock polyurethane foam comprising the steps of: providing a triol polyoxyalkylene polyether polyol having a plurality of internal blocks formed from oxyalkylene monomers with a plurality of terminal caps comprising ethylene oxide attached to said plurality of internal blocks, the internal blocks containing at least 80% by weight propylene oxide based on the total weight of all of the oxyalkylenes in said internal blocks and the amount of ethylene oxide in the terminal caps comprising from 5 to 25% by weight based on the total weight of the polyol, said polyol having a degree of unsaturation of less than or equal to 0.015 meq/g KOH; providing a toluene diisocyanate component; providing a catalyst; providing water as a blowing agent at a level of between 3 to 7 % by weight; and combining the polyol with the toluene diisocyanate component, the catalyst and the water to form a slabstock polyurethane foam.
In another embodiment, the present invention is a slabstock polyurethane foam comprising the reaction product of: a triol polyoxyalkylene polyether polyol having a plurality of internal blocks formed from oxyalkylene monomers with a plurality of terminal caps comprising ethylene oxide attached to said plurality of internal blocks, said internal blocks containing at least 80% by weight propylene oxide based on the total weight of all of said oxyalkylenes in said internal blocks and an amount of ethylene oxide in said terminal caps comprising from 5 to 25% by weight based on the total weight of said polyol, said polyol having a degree of unsaturation of less than or equal to 0.015 meq/g KOH combined with a toluene diisocyanate component in the presence of a catalyst, water at a level of between 3 to 7% by weight as a blowing agent, and, optionally, one or more surfactants.
Polyurethane foams produced using the method of the present invention have substantially improved indentation force deflection and resilience characteristics compared to a foam made with a similar polyol having a higher degree of unsaturation. The improved properties do not come at the expense of other physical characteristics of the foam, these are maintained.